Three dimensional packaging, such as a package-on-package (PoP) devices, presently require through mold interconnects in order to provide adequate stand-off heights. FIG. 1A, is an example of a prior art solution for providing the needed stand-off height. As shown, the through mold vias formed through a molding layer 160 are filled with solder bumps 144 to form the through mold interconnects. The solder bumps 144 block the opening and there is no path for moisture outgassing. As a result, the pressure below the solder bump increases until the pressure is finally able to lift the solder bumps 144 off of the substrate 101, as shown in FIG. 2B. Current solutions to prevent the solder bumps 144 from lifting off of the substrate 101 include overdrilling the cavity around the top side of the solder balls. However, overdrilling requires a larger pitch between through mold interconnects.
Furthermore, as the thicknesses of dies and substrates decrease, thermal effects are amplified, and the package becomes more susceptible to warpage. The use of through mold vias produces a non-continuous mold layer 160. Without mechanical continuity, the mold layer is not as effective at preventing warpage. Additionally, the mold layer 160 is typically a polymeric or epoxy material. Such materials have a large coefficient of thermal expansion (CTE) and a low elastic modulus. Accordingly, a thick layer is needed in order to provide mechanical support to the package in order to minimize warpage.